Well, the question seems to be answered several times here, some right and some wrong.
Below is a picture of what I use when I go fishing. It does include having a Jeep hooked up to them, and they run off the Jeep's electrical system. I think that if I were to run much more, I would scare the fish away! Each of these lights are 55 Watts and are more than enough for me to see what I am dragging out of the ocean. As for lighting up the entire beach, go with halogen's on stands (sears and wally world have sales on them a couple of times a year) and get you a little 1000 watt (1 kW) genie from honda or wherever. This doesn't answer your question, but gives you something else to work with. Good luck with fishing and hope you have lots of tight lines and fare weather this year!